System for the measurement, display and instrumental conditioning of electromyographic signals

ABSTRACT

A plurality of electrical contacts are applied to human beings to detect muscle (i.e. electromyographic, or E.M.G.) activity at various points of the body. Each of the multiplicity of resultant signals are amplified, filtered, rectified and converted to a pulse train. These pulse trains are integrated over programmable time periods and the multiplicity of integrated signals representative of muscle activity may be displayed on a multiplicity of output devices including audio and visual. In addition means are included to represent a reference signal corresponding to willful E.M.G. activity. This instrument is useful to provide exteroceptive signals to human beings whose proprioceptive mechanisms have been damaged by disease or other causes. By these means alternate neural pathways may be used to train or retrain human beings to proper willful activity and/or restoration of function.

United States Patent 1 Brudny [4 1 Sept. 16, 1975 [22] Filed:

211 Appl. No.: 422,129

[76] Inventor:

[52] US. Cl. I28/2.l M; 128/2.1 A [51] Int. Cl. A61B 5/04 [58] Field of Search 128/1 R, 2 N, 2 R, 2 S,

128/2.l A, 2.l B, 2.1 M, 2.1 P, 2.1 R, 2.1 Z,

419 R, 2.06 B, 2.06 G, 2.06 R, 2.05 O, 2.05 R; 340/407, 279

OTHER PUBLICATIONS V Pfeiffer et a1., Medical and Biological Engineering, Vol. 8, No. 2, March, 1970, pp. 209-211.

Primary Examiner-William E. Kamm Attorney, Agent, or FirmAlexander Mencher 57 ABSTRACT A plurality of electrical contacts are applied to human beings to detect muscle [i.e. electromyographic, or E.M.G.] activity at various points of the body. Each of the multiplicity of resultant signals are amplified, filtered, rectified and converted to a pulse train. These pulse trains are integrated over programmable time periods and the multiplicity of integrated signals representative of muscle activity'may be displayed on a multiplicity of output devices including audio and vi sual. In addition means are included to represent a ref- [56] References Cited erence signal corresponding to willful E.M.G. activity.

UNITED STATES TENTS This instrument is useful to provide exteroceptive sig- 2 647 508 8/1953 Pdavin 128/2 06 B nals to human beings whose proprioceptive mecha- 2'712'975 7/1955 Golseth aim. 128/21 M nisms have been damaged by disease or other causes. 3,641,993 2 1972 Gaarder et a1... 128/2. 1- M y these means alternate neural P y y be 3,753,433 8/1973 Bakerich et al.. l28/2.l B used to train or retrain human beings to proper willful 3,774,593 1 H1973 Hakata et a1. l28/2.1 M activity and/or restoration of function.

2 Claims, 8 Drawing Figures l l l l I ELECTRODES i l PREAMR l h l TRANSDUCER z 3 T 9 0P7'0 l VOL746'E 70 cmr pm ur R 4 ISOLA TOR l FREQUENCY I 5 com/12m? L POWER BAUER/ES SUPPLY TRANSDUCER POWER kssuumn 6 4 CHANNEL 1 TRANSDUCER PATENTEUS I 5 i975 3, 905 355 sum 5 [1F 8 SYSTEM FOR THE MEASUREMENT, DISPLAY AND INSTRUMENTAL CONDITIONING OF ELECTROMYOGRAPHIC SIGNALS BACKGROUND OF INVENTION This invention relates generally to the field of electronic computers, of a type employed for converting biological signals, from human .beings but not restricted exclusively to such use, to a variety of sensory display modes including visual and auditory.

The invention further contemplates a system for providing a combined diagnostic sensory display of muscular proprioceptive signals and a therapeutic comparative co-sensor display of continuous and willful muscular exteroceptive signals for differentiation of said signals by the subject and includes the steps of converting said proprioceptive signals into a continuous sensoryrecognizable form thereby inducing exteroceptive signals and converting said exteroceptive signals for modifying said continuous sensory-recognizable form so that the subject can judge the difference in the respective signals as a measure of therapeutic accomplishment.

In the past there have been various forms of apparatus constructed for diagnostic purposes, known as Electromyograph, for detection of electrical signals from the muscle. These devices are normally confined to laboratories only, are being used purely for diagnostic purposes and have little or no use in therapy.

There have been also in the past various forms of apparatus constructed for purposes of feedback of E.M.G. activity to subjects. Such apparatus have been used for teaching subjects relaxation of muscle activity. These devices failed uniformly to provide the necessary accuracy of time integration variables, failed to provide simultaneous display of more than one of muscles being examined, failed to provide built in features of instrumental learning, e. g. reference signal concept, failed to provide oscilloscopic displays of integrated muscle electrical activity.

In summary, the present available various apparatus failed to provide multiplicity of detection and display and multiplicity of therapeutic applications present in the proposed system.

In human beings mechanical output (work) is achieved as a result of a willful self-generated signal delivered to the sensory motor cortex from proprioceptive signals originating in muscles. In such instances the desire to produce work or motion is converted to an electrochemical signal which causes the contraction of certain appropriate muscle fibers and the relaxation of other appropriate muscles resulting in motion. The intensity of such muscle activity is transmitted back (by electrochemical means) to the brain or central nervous system where these intensity signals are compared to the signal. Any discrepancies are used to modulate or alter the contraction and relaxation of the muscles so as to bring the original stimulus and the resultant motion into conformity. This continuous process results in smooth motion. In humans afflicted with disease of physical impairment the intensity or presence of the muscle activity signals which are compared to the stimulus (referred to as proprioceptive feedback) may be altered in such a way as to prevent proper motion.

SUMMARY OF THE INVENTION The present disclosure relates to a device which will detect signals originating in the muscles, convert these signals into a form where the human being may detect them using visual and/or auditory senses rather than proprioceptive feedback, and thus permit proper comparison of the muscle response and motion stimulus.

It is among the principal objects of the present invention to provide an improved means for detecting and displaying biological signals from a multiplicity of biological sources in order to provide exteroceptive feedback to the organism for the smooth control of muscle action. Without such exteroceptive feedback, muscle action may be either spastic, paretic or otherwise impaired.

Yet another object of the invention lies in instantaneous display of units representative of muscle activity at any given time. These units can be recorded for the purpose of diagnosis, charting progress of recovery, prognosis, and collection of scientific data in research.

Another object of the invention lies in the provision of means for encoding and displaying a multiplicity of biological signals directly in units which are representative of muscle activity rather than arbitrary units which must be interpreted by the organism.

Yet another object of the invention lies in the provision of a multiplicity of displays from the multiplicity of biological muscle sources such that one source may be displayed in a visual mode while a second source may be displayed in an auditory mode.

Still another object of the present invention lies in the inclusion of a signal (herein called reference) by which a willful biological muscle activity may be represented in a variety of modalities. This reference can be used to provide exteroceptive information to the organism which is representative of its own willful biological muscle activity.

A further object of the present invention lies in the use of a representation of an organisms willful muscle activity (the reference) to do work in conjunction with a display of the signals from each of a multiplicity of muscles to provide means by which the organism may learn to produce smooth control of muscles which are otherwise impaired.

Yet another object of the present invention lies in the provision by which the difference between the representation of an organisms willful muscle activity and signals generated by the organisms muscles may be displayed in a variety of modalities.

These objects as well as other incidental ends and advantages will more fully appear in the progress of the following disclosure and be pointed out in the appended clairns.

Before entering into a detailed consideration of the structural aspects of the disclosure, the following discussion is believed apposite.

Electrochemical activity within a biological organism originating in muscle tissue may be detected either by inserting needle electrodes into the muscles or by placing suitable metal electrodes at the tissue-electrode interface. These signals consist of a time varying electrical intensity. They are generally larger and more frequent in occurrence when the muscle is contracted and they are smaller and less frequent in occurrence when the muscle is relaxed. In order to obtain a measure of the amount of work the muscle is doing, a computation of the work associated with the muscle activity is performed. This is accomplished by integrating the time varying muscle signal intensity. However, as the muscle signal may vary above and below some reference line,

the integral computation may produce a zero result while in fact considerable work is being done. Thus to measure the effective work the time varying muscle signal is first rectified. That is, the time varying intensities are made unidirectional in extent. This resultant signal is then integrated. Since the integral represents the area under the varying intensity signal and the electrical representation of the intensity has units of volts, the resultant unit of muscle activity is the volt-second. The intensities as detected in muscle tissue are generally much smaller than 1 volt. Generally these signals are in microvolts *volts). Thus the usual unit of muscle activity is the microvolt-second.

Integration of the rectified muscle signal can be performed by accumulating the effect of the varying intensity over a period of time. This can be accomplished by storing a charge in a capacitor. The current producing the charge can be made proportional to the muscle intensity. Another method of integrating the muscle signal, as depicted in the drawings and discussed herein, is to convert the muscle intensity into a sequence of electrical pulses. The frequency of these electrical pulses is proportional to the intensity of the muscle signal. These pulses may then be stored or accumulated in an electronic (or other) counter. The number of pulses counted in a given time interval is the equivalent of the integral of the rectified muscle signal.

BRIEF DESCRIPTION OF DRAWINGS With the foregoing discussion in mind, reference may now be had to the accompanying drawings, in which:

FIG. 1A is a schematic diagram of the entire device, showing two channels feeding to a central computer and display.

FIG. 1B is a schematic diagram showing, in somewhat more detail, the circuitry of a single channel of the device of FIG. 1A.

FIG. 1C is a schematic diagram showing, in somewhat more detail, the circuitry of the central computer and display of FIG. IA.

FIG. 2 is a schematic wiring diagram showing one channel of a two channel transducer.

FIG. 3 is a schematic wiring diagram showing a programmer.

FIG. 4 is a schematic wiring diagram showing a digital integrator.

FIG. 5 is a schematic wiring diagram showing display driver, reference source control, and recorder driver.

FIG. 6 is a schematic wiring diagram showing a comparator tone generator, and proportionality amplifier.

DESCRIPTION OF PREFERRED EMBODIMENT As can be seen in FIG. 1A the device comprises broadly: a system of electrodes 1; a system of transducers 2 (including, per FIG. 18, a pair of pre amps 5, gain adjust amps 6, half wave rectifiers 7, summers 8, and voltage to frequency converters 9); a system of opto isolators 3; and a central computer and display 4.

Inviting attention to FIGS. 1A, 1B, and 1C showing the preferred embodiment of the invention, electromyographic, or E.M.G., muscle signals from the electrode sets 1 associated with each of two or more channels (FIG. 1A) are first amplified, then integrated (FIG. 1D), and finally converted to electrical pulses whose frequency is proportional to the intensity of the muscle signals. These pulses are then fed to a central computer and display (4 in FIG. 1A), where the numher of pulses counted in a predetermined time interval is employed to provide a display (visual, auditory, and /or record) of a measure of the muscle activity. This display gives immediate information to the subject regarding his own muscle activity.

In keeping with another aspect of the invention, a reference signal, generated by a reference source or control (41 in FIG. 1C), may be established which corresponds to a willful biological muscle activity. This reference signal is then available for comparison with the display from the muscle signals in any of several predetermined modes. Thus, for example, by appropriate setting of the scope display select switch 36 and/or the mode switch 46 (FIG. 1C), as will be detailed subsequently, the actual display presented to the subject may correspond to the difference (or another predetermined relationship) between the muscle signal display and the reference signal display. By way of illustration, the subject may hear a sound only when his muscle signal exceeds the reference signal, or only when the muscle signal is less than that of the reference, or a sound which varies (either in pitch or intensity) in proportion to the difference between the two signals. Alternatively or simultaneously, the subject may be shown either or both displays, or only the difference between such displays.

To obtain electrical pulses of a frequency proportional to the intensity of muscle signals, a set of three electrodes associated with each amplification channel (FIG. 1A) is affixed to the subject. Electrical signals from each set are amplified, rectified, and integrated, and then converted to pulses having a frequency proportional to the intensity of the muscle signal (FIG. 1B).

Detailed operation of the device may be followed by considering elements shown in FIG. 1B and FIG. 1C. In FIG. 18, (one transducer is shown) the muscle signals are detected by induction into a system of electrodes 1 including individual electrodes 1A, 1B, and 1C. These signals are amplified in pre-amp 5. Further amplification is made in gain adjust amp. 6. Gain adjust amp. 6 also limits the frequency of occurrence of the signal to be within limits encountered in biological organisms. Half wave rectifier 7 converts all excursions of one polarity into excursions of the opposity polarity. Summer 8 combines the one directional excursions from half wave rectifier 7 and the bidirectional signal excursions from gain adjust amp. 6 in such a manner as to produce one directional signals from summer 8. The voltage to frequency converter 9 converts the intensity of the signal into a repetition of pulses whose frequency is proportional to the intensity of the signals coming from summer 8. The pulses from voltage to frequency converter 9 drive opto isolator 3. Opto isolator 3 upon receiving a pulse from voltage to frequency converter 9 will convert the electrical pulse to a light pulse. This light pulse can be transmitted to central computer and display 4. Thus, there is no wire connection between transducer 2 and central computer and display 4. This eliminates any hazard to the biological organism which might result from currents flowing in such a wire connection. Energy for the transducer is supplied by batteries 10. The voltage from these batteries is adjusted in power supply regulator 11 to a point where they are suitable for the elements of the transducer 2.

The light signals from opto isolator 3 are received in a light detector 12 shown in FIG. 1C. The detector 12 is an element of integrator 13. The detector 12 converts the light signals from opto isolator 3 into electrical pulses. The output of detector 12 is a repetitive sequence of pulses proportional in frequency to the rectified muscle signal intensity. When these pulses are summed up in counters 14, 15, l6, l7 and 18 under the control of full scale switch 19, and signals from programmer 20, the integral of the rectified muscle signal results.

The integrator 13 accepts these electrical pulses, collects them in a series of counters (16, 17, 18) during a preselected time period (shown in Table 1, below),

transfers the count to a series of store elements (29, 30, 3 l resets the counters to zero, and presents the stored count to a digital display 44. To understand how integrator 13 is controlled, consider the operation of programmer 20. Programmer 20 includes oscillator 21. Oscillator 21 produces a 4 Hz repetitive signal. This frequency of the oscillator signal is divided in half using FF 22 (flip flop). The output of FF 22 is further divided in half using FF 23. The output of FF 23 is again divided in half using FF 24. The output of FF 24 is dividcd by 5 using counter 25. Counter 26 directly divides the output of FF 23 by 5. The outputs of oscillator 21, FF 22, FF 23, FF 24, counter 25 and counter 26 have periods in accordance with Table 1.

These frequencies appear at integration time switch 27. One of these signals is selected from integration time switch 27 as the time interval over which the pulses representing the rectified muscle signal intensity are to be accumulated. This time signal passes to store one shot 28. Store one shot 28 produces a momentary signal for each repetition of the signal selected by integration time switch 27. When this occurs the count stored in counters 16, 17 and 18 of integrator 13 is transferred into store 29, 30, and 31 respectively.

Store elements 29, 30, and 31 taken together can accumulate a maximum of 999 pulses and a minimum of 000 pulses. The actual number of counts accumulated will depend on the rectified muscle intensity which produces pulses from detector 12 and the interaction of full scale switch 19 and counters 14 and 15. When store one shot 28 produces a signal which transfers the accumulated counts from counters 16, 17, and 18 into store 29, 30, and 31, a signal is also transmitted to reset one shot 32. This produces a momentary signal immedi' ately after the momentary signal produced by store one shot 28. Thus store one shot 28 and reset one shot 32 both produce a momentary signal at each repetition of the signal controlled by integration time switch 27. The store one shot 28 signal precedes the signal produced by reset one shot 32. The momentary signal produced by reset one shot 32 restores the accumulated count stored in counters 14, 15, 16, 17, 18 to zero. This occurs after the accumulated count of counters 16, 17, and 18 has been transferred to stores 29, and 31. Stores 29, 30, and 31 thus contain the number of counts accumulated by counters 16, 17 and 18 for the preceding period of time which has been selected by integration time switch 27. Each repetition of the time period selected by integration time switch 27 causes the stores 29, 30 and 31 to be updated from counters 16, 17, and 18 and causes counters 14, 15, 16, 17, and 18 to be reset.

It was noted above that the number of counts accumulated in counters 16, 17 and 18 in a time period selected by integration switch 27 depends on the number of counts being generated by detector 12, full scale switch 19 and counters 14 and 15. To see how this comes about make reference to Table 2.

TABLE 2 Counter Driven by Detector 12 Full Scale Switch 19 scale setting When full scale switch 19 is set to position 3 this corresponds to a full scale count of 999 microvolts of integrated rectified muscle signal. At the same time that the detector 12 is driving counter 14 (for full scale switch 19 scale setting 3) the full scale switch 19 also connects counter 14 to counter 15 and counter 15 to counter 16. 1f the original muscle signal had been microvolts, as an example, the detector 12 would produce a pulse repetition of 1,000 Hz. For scale setting 3 offull scale switch 19 counters 14, 15, 16, 17, and 18 are arranged to count 10 pulses and produce a carry to the next counter as they return to 0 (from 9).

Suppose that integration time switch 27 selects 1 second integration time. In 1 second detector 12 would produce 10,000 pulses. This would be counted in counters 14, 15, 16, 17, and 18. After 1 second, counter 18 would have 1 count and counters 17, l6, l5 and 14 should each have 0 counts. When the counts of counter l8, l7, and 16 are transferred to stores 31, 30 and 29 at the end of 1 second these elements (the stores) would then store a 1 in store 31; a zero in store 30, and a zero in store 29. 1f store 31 is interpreted as the most significant digit of the integral of rectified muscle signals, store 30 as the next most significant digit, and store 29 as the least significant digit, then the number 100 would appear in these stores. The number 100 is the indication that 100 microvolts existed for 1 second. Had integration time switch 27 selected 2 seconds, 20,000 pulses would have been produced by detector 12. The count in stores 31, 30, and 29 would be 200 after 2 seconds and this would correspond to an integral of 200 microvolt seconds. Thus stores 31, 30, and 29 contain a number which is the value of the integrated rectified muscle signal directly in microvoltseconds. Other arrangements of full scale switch 19 and integration time switch 27 similarly produce the exact integral value in stores 31, 30, and 29, directly in microvolt second units when multiplied by the setting on integration time switch 27 For various modes of display an analog signal rather than a digital signal is required. Such an analog signal, having a magnitude proportional to the integrated rectified muscle signal fed to the integrator 13 (FIG. 1C), is thus available for driving a scope display 39, a loud speaker 48, and/or an external analog recorder (via an amplifier 34).

The outputs of stores 31, and 29 drive digital to analog converter 33. This device produces an electrical output which is proportional to the number stored in stores 31, 30, and 29 at all times. The output of digital to analog converter 33 is thus an electrical signal (voltage) proportional to the integrated rectified muscle signal. The output of digital to analog converter 33 drives among other things amp. 34. Amp 34 adjusts the output of digital to analog converter 33 such that the output of amp. 34 is suitable for recording on a graphic or other recording device.

As noted previously, one of the display modes is the presentation of results on a scope 39. In keeping with this feature, controls are provided to allow the scope 39 to display any two of the preselected signals (i.e., from channel 1, from channel 2, and from the reference). To this end:

The output of digital to analog converter 33 also controls amp. 35. The output of amp. 35 is connected to scope display select switch 36. Amp. 37 and amp. 38 are also connected to scope display select switch 36. The scope display select switch 36 controls the signals which appear on scope display 39. The scope display select switch 36 controls which two signals appear on scope display 39. Scope display 39 is capable of displaying two signals as they can vary with time. The time base of scope display 39 is adjustable with sweep speed select 40. Control of the signals to be displayed is accomplished according to Table 3.

33 and amp. 35

Scope display 39 will display either the output of the channel 1 integrator 13 and a reference signal determined by reference control 41, or the output of channel 2 integrator 42 and the reference signal determined by reference control 41, or the output of both channel 1 integrator 13 and channel 2 integrator 42. The elements of channel 2 integrator 42 are identical in configuration to the elements of integrator 13 (channel 1).

displayed on digital display 44 the outputs of the stores in integrator 42 (channel 2) are transferred to digital display 44 by display select switch 43.

The remaining elements shown in FIG. 1C including channel select switch 45, comparator 49 (per FIG. 6, a Schmitt trigger discriminator 236), amp. 50, amp. 51, mode switch 46, tone generator 47 and speaker 48, are arranged to produce an audible tone which provides another modality to display the relation between a mu]- tiplicity of muscle sources and a signal representative of the willful stimulus produced by a human being. Channel select switch receives signals from digital to analog converter 33, an element of integrator 13, and from the corresponding digital to analog converter element of integrator 42. These inputs are voltages which are equivalent to the rectified integrated muscle signals. Channel select switch 45 determines which of these signals is to produce the audible tone. The signal selected by channel select switch 45 passes to amp. 50. A second input to amp. 50 is the reference signal produced by reference control 41. Amp. 50 produces a signal which is proportional to the difference between the Amp. 42A provides an identical function to amp. 34.

integrated rectified muscle signal from channel select switch 45 and reference control 41. The larger the diffcrence between the integrated rectified muscle signal and the reference signal, the greater the output of amp. 50. Comparator 49 receives the same inputs as amp. 50. Comparator 49 however produces either a zero signal or a larger intensity signal depending on the relative conditions of its input signals. If the integrated rectified muscle signal is smaller than the reference the comparator 49 produces its full magnitude output. Its output is not proportional to the difference but rather is present in its entirety as long as the integrated rectified muscle signal is smaller than the reference. If the integrated rectified muscle signal is equal to or larger than the reference, the comparator 49 will produce a zero signal. Amp. 51 inverts the sense of the comparator 49 signals. Thus the output of amp. 51 has no output when the integrated rectified muscle signal is smaller than the reference and has full output when the integrated rectified muscle signal is equal to or greater than the reference. A mode switch 46 determines which signal will pass to the tone generator 47. The signal passing to the tone generator is selected in accordance with Table 4.

TABLE 4 Tone generator 47 (i.e., a variable oscillator as shown in detail in FIG. 6) produces an output which is proportional to its input. The output of tone generator 47 drives speaker 48. Depending on the position of mode switch 46, speaker 48 will produce a tone in either of the following areas: a high intensity tone only when the integrated rectified muscle signal is equal to or greater than the reference, a high intensity tone only when the integrated rectified muscle signal is smaller than the reference, a tone whose intensity is proportional to the difierence between the integrated rectified muscle signal, or no tone when the mode switch 46 is set in the OFF position.

Exemplary circuit details for specific components and wiring for the system of FIGS. 1A, 1B, 1C are contained in FIGS. 2 through 6 inclusive. For convenient reference, nomenclature and numbering within the two groups of figures have been maintained. FIG. 2 is a schematic wiring diagram showing on channel of a two channel transducer. Signals from electrodes attached to a human subject are received by the pre amp at re- -sistors 52 and 53. These resistors together with the electrode capacitances of transistors 54 and 55 provide for attenuation of communication signals which might be induced in the signal leads. Transistors 54 and 55 are arranged to detect the difference between the two signal electrodes. Resistors 60, 61 and 62 act as biasing elements for transistors 54 and 55. Transistors 56 and 57 are arranged to amplify the output of transistors 54 and 55. Resistors 65 and 66 are bias elements along with resistors 68 and 69 for transistors 58 and 59. Transistors 58 and 59 serve to isolate transistors 56 and 57 from the remainder of the network. Resistors 70 and 71 and capacitors 72 and 73 serve to limit the lower repetition frequency of the incoming signals such that variations below Hz will not be amplified. Capacitor 63 and variable capacitor 64 serve to compensate for high frequency signals which may be present in both input leads. Variable resistor 67 compensates for common signals which may be present in both signal leads (the so called Common mode signal). Signals from the emitter of transistor 58 (via resistor 74) and the emitter of transistor 59 (via resistor 80) are coupled to transistors 77 and 78. These transistors provide additional amplication of the difference between incoming signals from the electrodes amplification Resistors 115A and 79 bias the transistors 77 and 78. Transistor 76 isolates transistors 77 and 78 from the remainder of the network. The output of the emitter of transistor 76 is coupled through capacitors 82 and 83 to the gain adjust amp. 6. The components up to resistor 84 in the signal path comprise the pre-amp 5. From the pre amp 5, signals are fed to a gain adjust amp 6 for amplitude control. Operational amplifier 86 (for example Type 776, Fairchild) with variable resistor 90 and resistor 84 comprise the means by which adjustments in the signal path may be accomplished. Capacitor 91 in conjunction with the aforementioned elements provides limits in the high frequency variation of the signal. Resistor 87 is a bias element and resistor 88 is an impedance compensation element.

The output of the gain adjust amp. 6 is transmitted via resistor 92 to the half wave rectifier 7 and via resistor 101 to the summer 8. When the output of gain adjust amp 6. is negative, operational amplifier 94 (Type 776, Fairchild) in conjunction with rectifiers 97 and 98, resistor 99, resistor 92, and biased resistors 95 and 96, produce zero volts at the junction of rectifier 98 and resistor 99 (the output of half wave rectifier 7). When the output of gain adjust amp. 6 is positive the output of half wave rectifier 7 is negative and of equal extent. The outputs of gain adjust amp. 6 (via resistor 101) and half we rectifier 7 (via resistor 100) are combined in summer 8.

Summer 8 produces the full wave-rectified version of the output of gain adjust amp. 6 in the following manner. When the output of gain adjust amp. 6 is negative,

zero volts appear at the output of half wave rectifier 7. Thus resistor sums zero current into the junction of resistors 101 and 100. Resistor 101 sums a current proportional to the negative signal at the output of gain adjust amp. 6. The output of summer 8 at the junction of operational amplifier 103 (Type 776, Fairchild) and resistor 104, is a voltage which is positive (operational amplifier 103 inverts the polarity of the current summed into resistors 101 and 100) and proportional to the sum of the voltages at the outputs of gain adjust amp. 6 and half wave rectifier 7. Two currents flow in resistors 101 and 100. The current in resistor 101 is proportional to the positive excursion of the output of gain adjust amp. 6. The current in resistor 100 is negative in direction. This is so because half wave rectifier 7 has inverted the signal from gain adjust amp 6. Resistor 101 and 100 are in the ratio of 2 to 1. The output of operational amplifier 103 is proportional to the sum of the currents flowing in resistors 101 and 100. The output of operational amplifier 103 is positive as it was for the case when the output of gain adjust amp. 6 was negative. The output of operational amplifier 103 is thus a full wave rectified signal proportional to the output of gain adjust amp. 6. Resistors 102, 105, and 106 bias the op amp 103.

The output of summer 8 is coupled via variable resistor 107 to voltage to frequency converter 9, which includes a voltage to frequency converter 109 (Type 4701, Teledyne). Variable resistor 107 adjusts the full scale frequency of voltage to frquency converter 109 while variable resistor 108 adjusts the absolute value of the low frequency operation -of voltage to frequency converter 109. The output of voltage to frequency converter 109 consists of pulses whose repetition rate is proportional to the output of summer 8.

The pulse signals from the voltage to frequency converter 9 are coupled via resistor. 110 to transistor 111, which delivers a pulse of current via resistor 112 to a light emitting diode 113 of opto isolator 3. Light from light emitting diode 113 is coupled (without wires) to photo transistor 114. Photo transistor 114 converts light pulses into electrical current flow and it forms part of detector 12 of the integrator 13 (or integrator 42 for the other transducer channel).

FIG. 3 is a schematic diagram of the programmer 20 of FIG. 1C. Transistor 118 in conjunction with resistors 115 and 116 and capacitor 117 oscillates at a frequency of 4 Hz. The output pulses are coupled via resistor 120 to transistor 121. Resistor 119 biases the transistor 118. Transistor 121 amplifies the pulses from transistor 111 and couples the amplified pulses via resistor 122 to integrated circuit 122A. Integrated circuit 122A contains 4 flip flops and associated gates arranged to act as a counter of 10. Integrated circuit 122A (Type 7490) divides the pulse repetition frequency of the pulses coming from transistor 121 by a factor of 10.

Integrated circuit 123 (Type 7473) consists of two flip flops, with each one able to divide its input by a factor of 2. Signals from integrated circuit 122A drive integrated circuit 123. Two outputs are available from integrated circuit 123. Each consists of pulses whose repetition rate is /2 and A respectively that of the output of integrated circuit 122A. The output of the second flip flop of integrated circuit 123 is coupled to two integrated circuits, namely and 124 (each Type 7490). Integrated circuit 125 (i.e., counter 26 of FIG.

TABLE Integrated Circuit Pulse Period of Output (secs) 122A .25 I23 .5, l 124 2, l() 125 5 Integrated circuit 129 (Type 7400) receives pulse signals from the integration time switch 27 via capacitor 128. Capacitor 128 differentiates the signal with resulting positive excursions being conducted to the power supply via diode 132. Negative excursions of pulse signals produced by capacitor 128 cause gates in integrated circuit 129 to be turned from a normally on state to a normally off state. This signal is coupled to two places. It is coupled to integrated circuit 137 where it is amplified and transmitted to store elements 31, 30 and 29.

The negative excursions of signals through capacitor 128 are restored to their normal level in a time determined by capacitor 128 and resistor 126 and variable resistor 127. Variable resistor 127 in conjunction with resistor 126 and capacitor 128 determine the duration of time during which the gates of integrated circuit 129 will remain cut off. This momentary signal in addition to being coupled to integrated circuit 137 (Type SP357, Signetics) is coupled via capacitor 136 to other gate elements in integrated circuit 129. A similar differentiation of signal takes place via capacitor 136; resistors 135, 133, 130 and diode 134. The resultant signal is a momentary signal occurring after the signal initiated by the signal from integration time selector switch 27. This momentary signal is coupled to integrated circuit 137 where it is amplified and transmitted to the counter elements 14, 15, 16, 17 and 18 of integrator 13 and the corresponding elements of integrator 42.

Detailed circuitry for the digital integrator 19, the counters 14-18, the stores 29-31 and the digital to analog converter 33 (i.e., 153) of FIG. 1C is shown in FIG. 4.

FIG. 4 is a schematic wiring diagram showing a digital integrator included in digital integrator 13 (or 42). An input sequence of pulses representative of rectified muscle signal intensity is transmitted from photo transistor 114 to resistor 138. The combination of diodes 139 and 140 prevents muscle signals from causing a false pulse. Resistors 141 and 142 are bias elements for transistor 143. Transistor 143 amplifies the pulses which are transmitted to integrated circuit 144 Type' 7400. This also amplifies the pulse signals and transmits them to the full scale switch 19.

Integrated circuits 145, 146, 147, 148 and 149 that is, counters 14, 15, 16, 17, and 18 of FIG. 1C; each Type 7490 are combinations of flip flops and gates arranged to produce states whose binary code represents the decimal digits 0 through 9. Upon returning from state 9 to state 0, a carry signal is produced. Thus integrated circuits 145, 146, 147, 148, and 149 can be 12 connected in serial order according to the position of full scale switch 19. The serial sequence of counting can be seen in Table 6.

TABLE 6 Setting of Full Scale Serial arrangement of integrated Switch 19 Circuits 145, 146, 147, 148 and 149 v The first element indicated in each line of the Table 6 is the element driven by the pulses originating in integrated circuit 144. Integrated circuits 150, 151, and 152 (i.e., stores 31, 30, 29, respectively, of FIG. 1C; each Type 7475) are arrangements of flip flops which can store a 4 bit binary code upon command. These elements store the binary coded decimal number which appears in elements 147, 148 and 149. The code is stored in 150, 151 and 152 upon command from store one shot 28. Integrated circuit 153 (Type DAC 372-12 BCD, Hybrid Systems Corp.) is a digital to analog converter. This receives signals from store elements 152, 151 and and proviides an analog representation of this binary coded decimal input at its output. Variable resistors 154 and 155 adjust the output voltage when the input is a binary coded representation of 000 and when the input is a binary coded representation of 999.

FIG. 5 is a schematic wiring diagram showing, in more detail, elements of FIG. 1C, including display drivers (i.e., amps 35, 37, 38), a reference source (i.e., reference control 41), and recorder drivers (amps 34 and 42A). Amp. 34 receives signals from the digital to analog converter 33. These are attenuated in resistor 154 and variable resistor 155 to cause them to be suitable for controlling either graphic recorders or magnetic tape recorders. Integrated circuit 157 and resistor 156 are used to provide a compatible driver for the various recording apparatus.

Amp. 42A is identical in function to amp. 34. Resistors 158, 159, and 160, and operational amplifier 161 perform identical functions as corresponding elements 154, 155, 156 and 157.

Amp. 35 receives signals from digital to analog converter 33. Resistors 174 and 175 suitably attenuate the signal such that for maximum input voltage from digital to analog converter 33 the deflection of the cathode ray tube electron beam observed on the scope display 39 is adjacent to a mark indicating full scale. Resistors 172 and 173 suitably attenuate the signal from digital to analog converter 33 (FIG. 1C) such that for zero signal from digital to analog converter 33 the deflection of the cathode ray tube electron beam observed on the scope display 39 is adjacent to a mark indicating zero signal. Operational amplifiers 177 and resistor 176 provide coupling means to scope display 39.

Amp. 37 includes elements 178, 179, 180, 181, 182 and 183 whose function is analogous to corresponding elements in amp. 34. Amp. 37 provides the same function for channel 2 signals that amp. 35 provides for channel 1 signals.

tional amplifier 171 which in combination with resistor 168 provides an output voltage with low equivalent source impedance. In addition to being transmitted to comparator 49 and amp. 50, the output of reference control 41 is transmitted to amp. 38. Amp. 38 contains elements 162, 163, 164, 165, 166 and 167 which function in an entirely analygous manner to the corresponding elements of amp. 35.

FIG. 6 is a schematic wiring diagram showing further details of FIG. 1C, including a proportionality amplifier 50, a comparator 236, and a tone generator 47. Signals representing the integrated rectified muscle signal are coupled via channel select switch 45 to resistor 185. Signals from the reference source 41 are coupled to re sistor 184. These signals are combined using operational amplifier 188 (Type 741), and resistors 186 and 187.

The output of operational amplifier 1S8 consists of the difference between the integrated rectified muscle signals and the reference. The amount of this difference is coupled via diode 190 and resistor 191 to the mode switch 46 (FIG. 1C) where it will drive the tone generator 47 when the mode switch 46 is set to proportional control. In addition, the output of operational amplifier 188 is coupled via resistor 189 to a Schmitt trigger circuit 236. This circuit determines when the reference signal is greater or less than the integrated rectified muscle signal and produces two different out put voltages for the two conditions. This is accomplished using resistors 189, 192, 193, and 195, diodes 196, 197, 198 and 199 and operational amplifier 194 (Type 741). Resistors 192 and 193 provide hysteresis in the operation of the network.

The output of the Schmitt trigger 236 is coupled via resistor 200 to an amplifier consisting of transistor 202 and resistor 201. The output of transistor 202 produces its maximum output when the reference is larger than the integrated rectified muscle signal and produces its minimum output when the reference is smaller than the integrated rectified muscle signal. In addition to transmitting this signal to the mode switch 46 the signal is coupled via diode 203 to another amplifier comprised of resistors 204, 206, and 208, diode 205, and transistor 207. These elements combine to invert the conditions at the output of transistor 202 in such a way that the output of transistor 207 will be a maximum when the output of transistor 202 is a minimum and the output of transistor 207 will be a minimum when the output of transistor 202 is a maximum. The output of transistor 207 is coupled to mode switch 46.

Tone generator 47 accepts signals from the mode switch 46. It accepts signals from either resistor 191, transistor 202, or transistor 207 or ground (when the mode switch 46 is in the off position) depending upon the position of mode switch 46. The signal is transmitted to the base of transistor 222. Transistor 222 and asof flip flops which divide the incoming pulse train by a factor of two. Thus the output pulses consist of square waves whose frequency is /z the incoming frequency (800 Hz for example). The outputs of integrated circuit 216 drive transistor 218 and 220 via resistors 217 and 218. Transistors 218 and 220 act as switches which either short the signals found at resistors 224 and 225 (when transistors 218 or 220 are closed) to ground or allow the signals found at resistors 224 and 225 to pass to resistors 226 and 227 (when transistors 218 or 220 are opened). The signals passing through resistors 226 and 227 are either zero (when transistors 218 or 220 are closed) or allow the signal originating at transistor 222 to pass to the operational amplifier 230. Since transistors 218 and 220 are driven from a flip flop in integrated circuit 216, they are turned on and off at different times. When transistor 218 is open, transistor 220 is closed and vice versa.

The combination of the operation of transistors 220 and 218 causes operational amplifier 230 and resistors 226, 227, 228 and 229 to act as an amplifier whose gain changes from negative to positive as transistors 220 and 218 are switches from on to off. The combination of transistors 218 and 220 and resistors 226, 227, 228, and 229 and operational amplifier 230 acts as a modulator of the signal present at the emitter of transistor 222. The magnitude of the signal at the output of operational amplifier 230 is proportional to the signal from the mode switch 46 and has a frequency determined by the oscillator transistor 212 and integrated circuit 216 (800 Hz for example). This signal (the output of opera tional amplifier 230) drives variable resistor 231. This adjusts the volume of the tone produced by speaker 48. The signal from the variable resistor or volume control, 231 is coupled to an amplifier consisting of transistors 232, 234, and 235 and resistor 233. The output of this amplifier (the junction of the emitters of transistors 234 and 235) drives speaker 48.

USES:

The normal sensory motor performance in health, is a closed loop servomechanism with continuity of sensory feedbackcontrol and with multisensory integration.

Any sizable deficit in the flow of afferent proprioceptive sensory information (feedback) will result in disturbance of skilled motor performance. Such disturbance is seen in a variety of neuromuscular disorders due to injury or disease, e.g., stroke, cerebral palsy, dystonia.

The proposed system, reflecting instantaneously the functional state of involved muscles and delivered to the central nervous system through intact sensory organs of vision and hearing, has been found of consider able therapeutic significance.

The proposed system is utilizing the known plasticity of central nervous system which is the perceptual mechanism that can deal with information supplied by structures not previously concerned with the analysis of a particular modality of sensory information.

The proposed system allows for substitution for the defect in the servomechanism of volitional movements through integration of substitute signals (exteroceptive instead of proprioceptive) The proposed system is reestablishing the integrity of sensory motor interaction and is allowing for learning of a new pattern of voluntary movements.

These new patterns of voluntary movement become permanently retained through processes of learning after the withdrawal of instrumental learning.

The uses of the proposed system will be of considerable therapeutic significance in treatment of many neuromuscular disorders, due to injury or disease, where there are clinical signs of decreased or absent sensory feedback from the muscles.

I claim:

1. An apparatus for obtaining and displaying muscle activity at a multiplicity of points on the human body, said device comprising:

a multiplicity of electrode sets adapted to be in contact with the skin, each of said electrode sets including two or more electrodes,

input means for receiving signals from said multiplicity of electrode sets,

amplification means for the amplification of said signals, full wave rectification means for said amplification of said signals for each of said multiplicity of signals representative of muscle activity,

conversion means for the conversion of said multiplicity of said full wave rectified signals into pulse signals whose frequency is proportional to said full wave rectified signals, the latter being representative of muscle activity,

isolation means connected to said conversion means by which said multiplicity of pulse signals is converted into a multiplicity of light signals,

a multiplicity of detection means associated with the multiplicity of light signals by which said light signals are converted into electrical pulses proportional to the repetition of said multiplicity of light signals,

a multiplicity of integration means including multipoint switching means connected to said multiplicity of detection means wherein a multiplicity of muscle signals is integrated by summation of the multiplicity of pulses produced by said multiplicity of detection means,

feedback means connected to said multiplicity of integration means wherein a multiplicity of signals subject to normal recognition by the normally functioning human senses are produced therefrom, said feedback means comprising:

a multiplicity of scale adjustment means wherein said integration may be adjusted in relation to the frequency of said pulses representative of muscle activity wherein the total number of accumulated pulses representative of the integrated muscle signal may be adjusted by insertion of said pulses into said multi-point switching means of said multiplicity of integration means,

a multiplicity of storage means by which the multiplicity of accumulated pulses associated with the said multiplicity of integration means may be stored for predetermined periods of time, such storage means retaining a continuous representation of the multiplicity of rectified muscle signals,

programming means whereby the contents of the multiplicity of storage means may be periodically changed and whereby the contents of said multiplicity of integration means may be initiated at zero, thereby preparing them for accumulation of pulses representative of muscle activity during a subsequent time period,

a multiplicity of conversion means whereby the said number of pulses stored in said multiplicity of storage means is converted therefrom into a voltage proportional to said number of pulses,

display means connected to any of the said multiplicity of storage means whereby the contents of said multiplicity of storage means may be displayed on a digital display device,

oscilloscope means including a cathode ray tube connected to said second mentioned multiplicity of conversion means whereby the voltage or signal from any and all of the said second mentioned multiplicity of conversion means may be displayed on said oscilloscope means as a continuous trace on the cathode ray tube of said oscilloscope means,

adjustable reference means connected to said cathode ray tube,

comparison means connected to any of said second mentioned multiplicity of conversion means wherein the signals from any of the second mentioned multiplicity of conversion means may be compared to said adjustable reference means, said comparison means producing signals proportional to the difference between the signals of said second mentioned multiplicity of conversion means and said adjustable reference means, and signals indicative of when said adjustable reference means is larger or smaller than the signals from said second mentioned conversion means,

audio means whereby the intensity of a tone may be adjusted in accordance with the output signal of the comparison means, such audio means being selected so as to be put at its maximum intensity when the signal from said second mentioned con version means is larger than said adjustable reference means, or when the signal from said second mentioned multiplicity of conversion means is smaller than said adjustable reference means, or whose intensity is proportional to the difference between said reference means signal and the signal from said second mentioned multiplicity of conversion means.

2. A device as in claim 1 wherein said adjustable reference means comprises:

an independent source of variable electrical voltage settable in magnitude so as to be representative of equivalent muscle activity and connected to said cathode ray tube to be displayable thereon as a continuous trace simultaneously with any of the signals of said second mentioned multiplicity of conversion means thereby providing a means for human beings to compare the signals from said second mentioned multiplicity of conversion means with said adjustable reference means representative of willful muscle activity. 

1. An apparatus for obtaining and displaying muscle activity at a multiplicity of points on the human body, said device comprising: a multiplicity of electrode sets adapted to be in contact with the skin, each of said electrode sets including two or more electrodes, input means for receiving signals from said multiplicity of electrode sets, amplification means for the amplification of said signals, full wave rectification means for said amplification of said signals for each of said multiplicity of signals representative of muscle activity, conversion means for the conversion of said multiplicity of said full wave rectified signals into pulse signals whose frequency is proportional to said full wave rectified signals, the latter being representative of muscle activity, isolation means connected to said conversion means by which said multiplicity of pulse signals is converted into a multiplicity of light signals, a multiplicity of detection means associated with the multiplicity of light signals by which said light signals are converted into electrical pulses proportional to the repetition of said multiplicity of light signals, a multiplicity of integration means including multi-point switching means connected to said multiplicity of detection means wherein a multiplicity of muscle signals is integrated by summation of the multiplicity of pulses produced by said multiplicity of detection means, feedback means connected to said multiplicity of integration means wherein a multiplicity of signals subject to normal recognition by the normally functioning human senses are produced therefrom, said feedback means comprising: a multiplicity of scale adjustment means wherein said integration may be adjusted in relation to the frequency of said pulses representative of muscle activity wherein the total number of accumulated pulses representative of the integrated muscle signal may be adjusted by insertion of said pulses into said multi-point switching means of said multiplicity of integration means, a multiplicity of storage means by which the multiplicity of accumulated pulses associated with the said multiplicity of integration means may be stored for predetermined periods of time, such storage means retaining a continuous representatioN of the multiplicity of rectified muscle signals, programming means whereby the contents of the multiplicity of storage means may be periodically changed and whereby the contents of said multiplicity of integration means may be initiated at zero, thereby preparing them for accumulation of pulses representative of muscle activity during a subsequent time period, a multiplicity of conversion means whereby the said number of pulses stored in said multiplicity of storage means is converted therefrom into a voltage proportional to said number of pulses, display means connected to any of the said multiplicity of storage means whereby the contents of said multiplicity of storage means may be displayed on a digital display device, oscilloscope means including a cathode ray tube connected to said second mentioned multiplicity of conversion means whereby the voltage or signal from any and all of the said second mentioned multiplicity of conversion means may be displayed on said oscilloscope means as a continuous trace on the cathode ray tube of said oscilloscope means, adjustable reference means connected to said cathode ray tube, comparison means connected to any of said second mentioned multiplicity of conversion means wherein the signals from any of the second mentioned multiplicity of conversion means may be compared to said adjustable reference means, said comparison means producing signals proportional to the difference between the signals of said second mentioned multiplicity of conversion means and said adjustable reference means, and signals indicative of when said adjustable reference means is larger or smaller than the signals from said second mentioned conversion means, audio means whereby the intensity of a tone may be adjusted in accordance with the output signal of the comparison means, such audio means being selected so as to be put at its maximum intensity when the signal from said second mentioned conversion means is larger than said adjustable reference means, or when the signal from said second mentioned multiplicity of conversion means is smaller than said adjustable reference means, or whose intensity is proportional to the difference between said reference means signal and the signal from said second mentioned multiplicity of conversion means.
 2. A device as in claim 1 wherein said adjustable reference means comprises: an independent source of variable electrical voltage settable in magnitude so as to be representative of equivalent muscle activity and connected to said cathode ray tube to be displayable thereon as a continuous trace simultaneously with any of the signals of said second mentioned multiplicity of conversion means thereby providing a means for human beings to compare the signals from said second mentioned multiplicity of conversion means with said adjustable reference means representative of willful muscle activity. 